Driving force transmission mechanism, image forming apparatus equipped with such a mechanism, and process unit of such an apparatus

Abstract

A drive transmission apparatus includes a first coupling portion having a polygonal shape; a second coupling portion having a hole portion which has a cross-sectional configuration larger than the first coupling portion, the hole portion being engageable with the first coupling portion; and a center shaft provided on the first coupling or the second coupling, the center shaft penetrating the other one of the first and second coupling.

Description

[0001]This application is a divisional application of U.S. patent application Ser. No. 09 / 978,213, filed Oct. 17, 2001, now U.S. Pat. No. 6,829,455, issued Dec. 7, 2004.FIELD OF THE INVENTION AND RELATED ART[0002]The present invention relates to an image forming apparatus equipped with a driving force transmission mechanism, and a process unit used by such an image forming apparatus.[0003]Conventionally, a driving system for driving a photoconductive drum, as an image bearing member, of an image forming apparatus such as a copying machine, a printer, or the like comprises: a driving gear, which receives the driving force from the motor of the main assembly of the image forming apparatus, and transmits the driving force; and a gear shaft, which is coaxial with the driving gear, and rotates with the driving gear. There are two methods for driving a photoconductive drum with the use of such a driving system: a driving method which employs a driving shaft with a coupling, and a driving ...

AI Technical Summary

Benefits of technology

[0014]Thus, the primary object of the present invention is to provide a driving force transmission mechanism, which assures that even when the contact between the female and male type portions of a coupling is disturbed by a force other than the force transmitted to the driven system from a driving system, the normal contact is maintained between the female and male type portions of the coupling, so that the cylindrical member of a driven system remains properly supported, and the accuracy of the alignment between the driven and driving systems is maintained regardless of the size of the play between the female and male type portions when they are in engagement with each other.

Problems solved by technology

However, a coupling based driving method is inferior to a direct driving method in terms of driving force transmission accuracy; in other words, there is a concern that a coupling based driving method suffers from the problem regarding the angle at which two shafts are connected to each other by a coupling, the problem regarding how two shafts are aligned with each other by a coupling, or the like problems.

When an image forming apparatus suffers from the problems described above, an image becomes misaligned relative to a recording medium, degrading image quality.

This problem is particularly conspicuous in an image forming apparatus which forms a color image on recording medium by placing a plurality of images different in color, in layers.

The above described coupling, however, suffers from the problem that as the driven system is subjected to a force other than the force transmitted from the driving system, the contact between the two systems is disturbed.

More specifically, two shafts to which the female and male type portions of the aforementioned coupling are attached one for one are kept aligned with bach other by the contact between the two members of the coupling, and therefore, as the contact between the two members is disturbed, the two shafts become misaligned with each other, causing an image to be misaligned with the recording medium, as the image is formed.

This has been a significant problem.

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